int * function(void)???

kalleanka · 08-01-2006, 08:21 AM

why does some functions have void declared as this:
int * function(void)
{
...code

}

I do not get the point. Why not without the void?

dmail · 08-01-2006, 08:24 AM

Somebody will correct me if I am wrong, but I believe it's related to old c code. If there was not a void as a parameter and just empty parentheses it could take a number of arguments. (think I remember reading this, but it may be a lie lol).

kalleanka · 08-01-2006, 08:33 AM

sounds reasonable.

dmail · 08-01-2006, 08:41 AM

Heres some info on the subject from The C programming language K&R

Quote:

...A note of history: the biggest change between ANSI C and earlier versions is how functions
are declared and defined. In the original definition of C, the power function would have been
written like this:

/* power: raise base to n-th power; n >= 0 */
/* (old-style version) */
power(base, n)
int base, n;
{
int i, p;
p = 1;
for (i = 1; i <= n; ++i)
p = p * base;
return p;
}
The parameters are named between the parentheses, and their types are declared before
opening the left brace; undeclared parameters are taken as int. (The body of the function is
the same as before.)
The declaration of power at the beginning of the program would have looked like this:
int power();

No parameter list was permitted, so the compiler could not readily check that power was being
called correctly. Indeed, since by default power would have been assumed to return an int, the
entire declaration might well have been omitted.

Hmm so I think I was sort of correct.

jim mcnamara · 08-01-2006, 09:07 AM

Code:

int foo()......

to declare a function then it can be passed any number of arguments. You can also do the same with function pointers
Don't do this as a regular thing it will bite you in the end.:

Code:

int foo1(int a, int b)
{
	return a+b;
}

int foo2(int a)
{
	return a;
}

int main(int argc, char *argv[])
{
	typedef int (*F)();
	F test;
	test=foo1;
	printf("%d\n",test(1,2));
	test=foo2;
	printf("%d\n",test(2));
	return 0;
}

marozsas · 08-01-2006, 09:37 AM

The type void in function parameter is to make clear the function has no arguments and the type void in function type is to make clear the function returns nothing.

In old C, a function could be declared as

func();

In this declaration the implicit return type is integer and we could say nothing about its parameters (it could be declared with parameters later in the code). To avoid such indetermination the void type was introduced.